LevelOne GTL-2691 User Manual

Page 162

HAPTER

| Interface Configuration

Port Configuration

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When using auto-negotiation, the optimal settings will be negotiated

between the link partners based on their advertised capabilities. To set

the speed, duplex mode, or flow control under auto-negotiation, the

required operation modes must be specified in the capabilities list for

an interface.

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The 1000BASE-T and 10GBASE-T standard does not support forced

mode. Auto-negotiation should always be used to establish a

connection over any 1000BASE-T or 10GBASE-T port or trunk. If not

used, the success of the link process cannot be guaranteed when

connecting to other types of switches.

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The Speed/Duplex mode is fixed at 1000full on the Gigabit SFP ports,
and at 10Gfull on the 10 Gigabit ports. When auto-negotiation is

enabled, the only attributes which can be advertised include flow

control and symmetric pause frames.

Using Jumbo Frames

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Use the jumbo frame attribute on the System > Capability page to

enable or disable jumbo frames for all Gigabit and 10 Gigabit Ethernet

ports. Then specify the required MTU size for a specific interface on the

port configuration page.

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The comparison of packet size against the configured port MTU

considers only the incoming packet size, and is not affected by the fact

that an ingress port is a tagged port or a QinQ ingress port. In other

words, any additional size (for example, a tagged field of 4 bytes added

by the chip) will not be considered when comparing the egress packet’s

size against the configured MTU.

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When pinging the switch from an external device, information added for

the Ethernet header can increase the packet size by at least 42 bytes

for an untagged packet, and 46 bytes for a tagged packet. If the

adjusted frame size exceeds the configured port MTU, the switch will

not respond to the ping message.

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For other traffic types, calculation of overall frame size is basically the

same, including the additional header fields SA(6) + DA(6) + Type(2) +

VLAN-Tag(4) (for tagged packets, for untaqged packets, the 4-byte

field will not be added by switch), and the payload. This should all be

less than the configured port MTU, including the CRC at the end of the

frame.

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For QinQ, the overall frame size is still calculated as described above,

and does not add the length of the second tag to the frame.

ARAMETERS

These parameters are displayed:

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Port – Port identifier.

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Type – Indicates the port type. (1000BASE-T, 1000BASE SFP,

10GBASE-T, 10GBASE XFP)